1. BIOLOGY
AL Teaching Notes
CELL STRUCTURE

2. Cell Structure Cell wall Cell membrane
protoplasm - the living contents within the cell: nucleus and cytoplasm

3. Cell membrane Chemical components :consists of protein and lipid
Structure: Two layers of lipid sandwiched between two protein layers

4. Function of cell membrane
Act as a partially permeable barrier controlling the movement of substances between the cell and the surrounding
Act as support
Act as enzyme which catalyzes the chemical reaction within the cell membrane
Act as carriers in transporting substance across the membrane
Act as recognition center

5. The Structure of Cell membrane

6. Nucleus Contains chromatin which is involved in nuclear division
Contains a nucleolus

7. Structure of Nucleus
Enclosed by and envelope of two membranes that is perforated by nuclear pores

8. Function of Nucleus Necessary for survival of a cell
Controls all the activities of the cell, cellular function, cell division and heredity

9. Nuclear membrane Doubled layer Similar structure as cell membrane
Continuous with E.R.
With microscopic pores for exchange of materials between nucleus and cytoplasm

10. Nucleoplasm Nuclear sap Gel-like Denser than cytoplasm
Contains proteins, nucleotides and ions

11. Chromatin Consists of DNA and protein ( histone )
Condense to rod-shape chromosome just prior to nuclear division
Carry genetic materials which determine organisms’ characteristics and transmit these characteristics to next generations

12. Nucleolus Composed of DNA mainly
Act as the manufacturing site of ribosomal DNA (rDNA) and ribosomes

13. Ribosomes
Particles synthesis in nucleolus and then pass through the nuclear pores to the cytoplasm
Made of protein and rDNA
The site for protein synthesis

14. Endoplasm Reticulum ( E.R.)
A system of parallel flattened membrane-bounded sacs called cisternae
Continuous with the outer membrane of the nuclear envelope
Act as an intracellular transport system
There are two types of E.R - Rough ER and smooth ER

15. Rough E.R. Ribosomes are attached to its surface
Transports proteins made by the ribosomes through the cisternae to smooth ER and then to Golgi appartus for futher modification

16. Smooth E.R. Without ribosomes attached to its surface Transport lipids
Synthesis of lipids and steriod

17. Diagram of Golgi

18. Golgi Apparatus Usually located near the nucleus
consists of stacks of flattened membrane bounded sacs called cisternae and many vesicles
At one end of the stacks new cisternae are constantly formed by fusion of vesicles pinched from smooth ER; at the other end, small Golgi vesicles are pinched off constantly
Transport in vesicles of many cell materials, such as enzymes form ER
Involved in secretion and lysosome formation

19. Lysosomes A spherical sac bounded by a single membrane
Contain digestive (hydrolytic) enzymes
Intracellular digestion of food materials eg. Amoeba
Destroy the worn-out organelles inside cell
For self-destruction of cells in developmental process

20. Mitochondrion I
Surrounded by an envelope of two membranes, the inner being folded to form cristae
Contains a matrix with respiratory enzymes for the Kreb’s cycle
Rich in cell which require large amont of energy such as sperm tail, muscle cell
cristae
matrix
outer
membrane
inner membrane

21. Mitochondion II
The cristae increase the surface area for attachment of respiratory enzymes for the electron transfer reactions
In aerobic respiration, cristae are the sites of oxidative phosporylation and electron transport

22. Function of Mitochondrion
Act as power house of a cell
The energy releasing reactions of respiration occur in matrix and on the cristae

23. Centrioles Adjacent to nucleus
Internal structure of a centriole is similar to that of basal body of a cilium, with 9 micotubules
Forming the spindle fibres and microtubules during nuclear division to control the separation of chromatids and chromosome

24. Microtubule Act as cytoskeleton which support the cell
Involves in the movement of substances inside the cell
Forming the spindle fibres which involve in the separation of chromatids and chromosome

25. Cell wall Only found in plant cells Rigid and rather permeable
Made of cellulose
Usually modified by lignin
with pores which are penetrated by plasmmodesmata

26. Function of Cell wall
Provides mechanical support and protection of the cell
Allows a pressure potential to be developed which aids in support
Prevent osmotic bursting of the cell

27. Chloroplast
Large plasmid containing chlorophyll which absorb light for photosynthesis
Bounded by two membrane
Consists of chloroplast envelope, stroma, lamella and granum

28. Vacuole Absence or small in animal cells
Common and large in plant cells
The enclosing membrane is called tonoplast
Contain the internal cell sap which is a concentrated solution consists of water, sugar, salts, fat, oils, proteins and pigment

29. Function of Vacuole Store various substances eg. Food and wastes
Maintenance of turgor for support
Contain hydrolytic enzymes to acts as lysosomes during life and cause autolysis after death

30. Plant Histology Parenchyma Collenchyma Sclerenchyma Xylem Tissue
Phloem Tissue

31. Parenchyma Plant cells with thin cell wall and living protoplasm
Roughly isodiametric with intercellular spaces
Found in cortex and pith of stems and root, mesophyll of leaves and packing tissues in xylem and phloem

32. Function of Parenchyma
Act as packing tissues between more specialized tissues
Turgidity of these cells can provide support in herbaceous plant
Store food
Intercellular air spaces allow gaseous exchange
Metabolically active
Their cell walls are important pathway for the water and mineral salts through the plant

33. Collenchyma
Characterized by the deposition of extra cellulose at the corners of the cells so have thickening cell wall of their corners
They are living cells
Found in regions beneath the epidermis of stem (hypodermis) and near the vascular tissues, eg, midrib of leaves

34. Sclerenchyma
Plant cells with uniformly thickened cell wall which is usually lignified
They are dead cells
Support the cells
There are two types: fibres and Sclerids

35. Fibre Long narrow cell shape with tapering ends, wall with few piths
Found in cortex, pericycle, vascular tissues, surrounding vascular bundles

36. Sclereids
Shorter, vary much in shape, may be spherical, polyhedral, elongated or branched with numerous pits
Found in almost everywhere in plant body, especially in cortex, phloem of stems and roots, in fruit wall and seed coat
Act as main cell type for mechanical support

37. Xylem Tissue
Tracheary elements (tracheids, vessels) which are dead and empty cells for conducting water and support

38. Tracheids
Narrow elongated cell with finely tapering ends, without protoplasm at maturity, with heavily lignified and pitted secondary cell wall
Passage of water from cell to cell is facilitated through pit-pairs which allow lateral transport of water
Act as the only water conducting elements in gymnosperms and primitive vascular plant; small amount in angiosperms

39. Vessel I
Long, pipe-like cell shape, with complete or incomplete perforation at the end wall
Without protoplasm at maturity
Join each other at perforated end walls to form longitudinal conducting tubes
Shorter, greater in diameter than tracheids

40. Vessel II
Water moves from cell to cell through perforations and pit pairs
Cell wall lignified and strengthened to prevent collapse
More specialized for water conducting than tracheids
Only present in angiosperms

41. Diagram of Phloem

42. Phloem Tissue
Sieve elements (sieve cells, sieve tube elements) for conduction of food materials
Sieve elements are elongated cells, cell wall with sieve areas
Sieve elements is absence of nucleus, tonoplast, decrease in number of ER and ribosomes, with thin layer cytoplasm to facilitate the translocation of food

43. Sieve Cell With sieve areas evenly distributed
Present in gymnosperms and lower vascular plant

44. Sieve Tube Element Located on the end walls called sieve plates
Connected by sieve plates with each other to form sieve tube
Present in angiosperms
With companion cell to help translocation of food

45. Blood cell
Is a specialized connective tissue for transportation of materials and body defence
include fluid medium (plasma 55%) and cellular constituents (erythrocytes, leukocytes and thrombocytes 45%)

46. Skeletal muscle Innervated by the voluntary part of nervous system
contraction is neurogenic required nervous stimulation
contract and fatigue rapidly
attached to the skeleton
long, cylindrical with tapering or rounded ends

47. Functions of skeleton muscle
for the maintenance of posture
for locomotion and movements of body parts

48. Neurones Including cell body and nerve fibres located in C.N.S
cell body is stellate in shape
nerve fibres are protoplasmic extensions of cell body, including dendrons and axon

49. Nerve
a group of nerve fibres bound together by connective tissues lying outside C.N.S
including sensory nerve, motor nerve and mixed nerve